JPH09223825A - Piezoelectric application element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent any oxide film from being formed between an elastic body and an electro mechanical conversion element, by interposing between the elastic body and the electromechanical conversion element an electrode made of a high-melting-point metal hard to be oxidized, a high-melting-point nobel metal or their alloy. SOLUTION: Arranging continuously many protruding portions 3a on the edge portion of one surface side of an annular elastic body 3, on the other surface side thereof, a lower electrode 5a comprising a Ta layer and Pt layer is formed by sputtering. On the lower electrode 5a, a piezoelectric material layer 4 made of lead titanate zirconate is formed by sputtering. On the surface of the piezoelectric material layer 4, an upper electrode 5b comprising a Ta layer and Pt layer which is divided into many portions in its circumferential direction is formed by sputtering. When the electrode 5a is made of such a high-melting-point metal hard to be oxidized as nickel, chrome and cobalt, such a high-melting-point nobel metal as platinum and palladium or their alloy, suppressing the generated oxidation quantity of the electrode 5a by its heat treatment, any oxide film can be prevented from being formed between the elastic body 3 and the electromechanical conversion element 4, 5b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric device having an electromechanical transducer having an elastic body formed on a surface thereof.

[0002]

2. Description of the Related Art Conventionally, an electric machine such as a piezoelectric element, a magnetostrictive element or an electrostrictive element is formed on the surface of an elastic body which constitutes a piezoelectric application element utilizing a piezoelectric effect such as an actuator such as a vibration actuator, a mechanical filter or a gyro. In order to form the conversion element, the electromechanical conversion element is formed into a thin plate by a separate part made of, for example, lead zirconate titanate (PZT), and the formed electromechanical conversion element is bonded to the surface of the elastic body, for example. It was pasted by.

However, when the electromechanical conversion element is attached to the surface of the elastic body as described above, the thickness of the electromechanical conversion element cannot be reduced to a predetermined value or less due to restrictions in manufacturing technology. Therefore, in order to secure the output of the above-mentioned piezoelectric application element at a desired value, it is necessary to apply a high driving voltage, which makes it difficult to downsize the entire device.

Therefore, for example, Japanese Patent Application Laid-Open No. 63-28279 discloses a piezoelectric element made of lead zirconate titanate.
A vibration actuator has been proposed in which a thin film is formed on the surface of an elastic body by a thin film forming technique such as vapor deposition or sputtering.

[0005]

By the way, in order that the electromechanical conversion element formed into a thin film on the surface of the elastic body by the thin film forming technique has piezoelectric characteristics, lead zirconate titanate is used for the piezoelectric element. In the case of constructing, the crystal structure of lead zirconate titanate needs to be a perovskite type.

That is, in order to form an electromechanical conversion element by the thin film forming technique, usually, a thin film is formed in a high temperature region or an amorphous thin film is formed in a low temperature region and then heat treatment is performed. The obtained crystal structure remarkably differs depending on the film forming temperature and the heat treatment temperature.

FIG. 12 is a graph showing a difference in crystal structure due to a difference in film forming temperature or heat treatment temperature. As shown in the figure, the heat treatment temperature is from about room temperature to 300 ° C., or almost without heat treatment, the heat treatment temperature is 4
When the temperature is around 00 ° C, it is mainly a pyrochlore type, and when the heat treatment temperature is around 500 ° C, the pyrochlore type and the perovskite type are mixed, and the heat treatment temperature is 600 ° C.
When it becomes above, it becomes a perovskite type mainly.

As described above, when the film formation or heat treatment is performed in a high temperature range and the crystal phase is formed at a high temperature of 600 ° C. or higher, only the perovskite phase having piezoelectricity is generated, but the heat treatment is performed in a low temperature range. If it is carried out and the formation of the crystal phase is not carried out at a sufficiently high temperature, a pyrochlore phase having no piezoelectric property is generated together with the perovskite phase.

Therefore, in order for the electromechanical conversion element formed by the thin film forming technique to have piezoelectricity, the piezoelectric layer is formed in a high temperature region of, for example, 600 ° C. or higher, or a thin film formed at a low temperature. It is necessary to subject the layer to heat treatment in a high temperature range of, for example, 600 ° C. or higher.

Further, most of the electromechanical transducers used are lead-based oxide materials as typified by lead zirconate titanate because the displacement amount per applied electric field is large. Nearly half of the cations are lead ions, which are easily reduced. Therefore, for example, even when the heat treatment is performed after the phase is formed in a high temperature region of 600 ° C. or higher, the atmosphere is rich in oxygen.

Therefore, when an iron-based alloy such as stainless steel is used for the elastic body, if the film formation or heat treatment is performed in a high temperature range of, for example, 600 ° C. or higher, the surface of the elastic body is oxidized or electromechanical conversion is performed. There is a high possibility that a chemical reaction represented by mass transfer such as diffusion of oxygen atoms or lead atoms occurs between the element and the elastic body. Due to such a chemical reaction, an oxide layer is formed on the surface of the elastic body, or the chemical composition near the interface between the elastic body and the electromechanical conversion element is changed, so that the piezoelectric characteristics are deteriorated or the electromechanical conversion element is reduced. There is a possibility that the adhesion strength between the elastic body and the elastic body is significantly reduced.

Further, in order to match the two natural frequencies generated in the elastic body, it is necessary to accurately grasp the elastic modulus and density of the electromechanical conversion element, and further to calculate. However, in the conventional technology in which the electromechanical conversion element is attached as a separate component, the adhesive layer that is inevitably present between the elastic body and the electromechanical conversion element affects the calculated value. There was an error, and the frequencies could not be matched exactly.

[0013]

The present invention relates to a piezoelectric applied element having an elastic body on the surface of which an electromechanical conversion element is formed by a thin film forming technique, and the piezoelectric applied element is provided between the elastic body and the piezoelectric applied element. An electrode made of a metal having a high melting point and difficult to oxidize, a noble metal having a high melting point, or an alloy thereof is arranged.

The above-mentioned "thin film forming technique" in the present invention refers to a technique for forming a functional thin film such as vapor deposition, sputtering, CVD and sol-gel method. The thin film formed has a thickness of about 1 μm, which is 1/100 or less of the thickness of the conventional electromechanical transducer.

The "electromechanical conversion element" in the present invention includes a piezoelectric element, a magnetostrictive element, an electrostrictive element and the like. Further, in the present invention, "metal having a high melting point and difficult to oxidize" means nickel, chromium, cobalt, etc., and "noble metal having a high melting point" means platinum, rhenium, rhodium, palladium and the like.

That is, metal atoms having a low melting point, such as iron, aluminum, and copper, are extremely likely to combine with oxygen atoms and oxidize in a high temperature environment. Moreover, since these atoms have a low melting point, the diffusion of atoms is extremely easy to occur in a high temperature range where a perovskite phase is stably generated.

Therefore, forming an electrode from these metals or an alloy containing a large amount of these metals, and forming an electromechanical conversion element stable at high temperature such as a perovskite type on the surface thereof is particularly effective when it is made of titanium. In the case of lead-based oxides such as lead zirconate oxide, treatment in a reducing environment is impossible, and since the electromechanical conversion element itself is an oxide, oxidation of the electrodes cannot be avoided. Therefore, it is extremely difficult.

Further, during the heat treatment, the atoms of the electrode are in a state of being easily diffused, and the lead atoms in the electromechanical conversion element also have an extremely low melting point. Therefore, diffusion of lead atoms from the electromechanical conversion element to the elastic body is performed. Can't be avoided.

The formation of an oxide film on the surface of the elastic body or at the interface between the elastic body and the electromechanical conversion element reduces the adhesion strength between the electromechanical conversion element and the elastic body, and facilitates the peeling of the electromechanical conversion element. In particular, the electromechanical conversion element hardly adheres to the surface of the elastic body that has been oxidized, especially when it is generated in a high temperature range.

Further, an elastic oxide layer is formed at the interface between the elastic body and the electromechanical conversion element, a diffusion layer is formed by diffusing lead atoms into the elastic body, and the diffusion layer is formed in the vicinity of the interface. The formation of a low dielectric constant dielectric layer other than the electrode between the elastic body and the electromechanical conversion element, such as the formation of a lead deficient layer in the electromechanical conversion element, results in the piezoelectric element. The effect will be significantly impaired.

On the other hand, when the electrode is made of a metal such as nickel, chromium or cobalt which has a high melting point and is difficult to oxidize, or a noble metal having a high melting point such as platinum, rhenium, rhodium or palladium, or an alloy thereof, high temperature is used. Since it is difficult to form an oxide layer on the surface even in the case of film formation, it is difficult to form a diffusion layer or the like between the elastic body and the electromechanical conversion element, and also during heat treatment, substance diffusion occurs between the elastic body and the piezoelectric element. Since it is difficult, there is no fear that the piezoelectric effect will be hindered.

As described above, in the piezoelectric applied element according to the present invention, the electrode arranged between the elastic body and the electromechanical conversion element is a metal having a high melting point and difficult to oxidize, a noble metal having a high melting point, or these metals. Since it is formed of an alloy, the amount of oxidation of the electrode due to heat treatment is suppressed, and it becomes difficult to form an oxide film between the elastic body and the electromechanical conversion element.

Further, by heat treatment, the electrode constituent atoms are blocked from the elastic body to the electromechanical conversion element by the electrode of the present invention, the amount of diffusion is reduced, and a diffusion layer is formed between the elastic body and the electromechanical conversion element. It becomes difficult to be formed.

Further, since the thickness of the conventional electromechanical transducer is 1/100 or less and the adhesive layer is not interposed, the vibration absorbing layer due to the adhesive layer does not exist, and the error component in the calculation of the natural frequency is not included. Is reduced.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) The present invention will be described in more detail below with reference to the accompanying drawings.

FIG. 1 is an exploded perspective view showing a first embodiment in which the present invention is applied to an ultrasonic actuator which is an example of a vibration actuator, and FIG. 2 shows an upper electrode formed in the first embodiment. It is a top view which shows an elastic body.
As shown in FIG. 1, a large number of convex portions 3 are formed on the edge portion on one plane side.
A lower electrode 5a composed of a Ta layer and a Pt layer is formed by sputtering on the other flat surface side of the annular elastic body 3 in which a is continuously provided, and lead zirconate titanate ( A piezoelectric layer 4 of PZT) is formed by sputtering.

On the surface of the piezoelectric layer 4, as shown in FIG. 2, an upper electrode 5b composed of a Ta layer and a Pt layer divided in the circumferential direction is formed by sputtering.

The Ta layer is formed in order to secure sufficient adhesion strength between the Pt layer and the substrate. The Ta layer itself is also a substance that hardly reacts with the substrate and can be a constituent material of the electrode. However, if the piezoelectric layer 4 made of PZT is provided directly on the Ta layer because it is easily oxidized, oxygen in the piezoelectric layer 4 made of PZT may be absorbed.

The conditions for forming the lower electrode 5a composed of the Ta layer and the Pt layer on one plane of the elastic body 3 by the sputtering method are listed below. (Ta layer) Using a Ta target, sputtering was performed by the RF sputtering method under the following conditions.

RF power: 1.5 W / cm ² Sputtering gas: Ar gas 1 Pa Sputtering time: 10 minutes Substrate temperature: 200 ° C.

(Pt layer) Using a Pt target, sputtering was performed by the RF sputtering method under the following conditions.

RF power: 1.5 W / cm ² Sputter gas: Ar gas 1 Pa Sputter time: 30 minutes Substrate temperature: 200 ° C.

The film thickness of the lower electrode 5a is about 1 μm. Next, the piezoelectric layer 4 on the surface of the lower electrode 5a will be described. The conditions for forming the piezoelectric layer 4 are listed below.

(PZT layer) PbO: ZrO ₂ : TiO ₂
Sputtering was performed by the RF sputtering method under the following conditions, using a target of = 1: 0.5: 0.5 (molar ratio).

RF power: 2 W / cm ² Sputtering gas: Ar / O ₂ = 90/10, 1 Pa Sputtering time: 4 hours Substrate temperature: 600 ° C.

Further, an upper electrode 5b made of a rectangular Ta layer and a Pt layer was formed on the surface of the piezoelectric layer 4 by sputtering. Also, this upper electrode 5b
Was masked during sputtering, and was formed into a plurality of circumferentially divided portions as shown in FIG.

The elastic body 3 is formed on the piezoelectric layer 4 from a driving voltage device (not shown) via the upper electrode 5a and the upper electrode 5b.
When a drive voltage is applied, a progressive vibration wave is generated in the above-mentioned convex portion 3a.

An annular rotor member 1 rotatably supported by a support mechanism (not shown) is attached to one of the flat surfaces of the sliding member 2 on the above-mentioned convex portion 3a of the elastic body 3. Through pressure contact.

Further, in order to correct the deformation of the elastic body 3 due to sputtering, the elastic body 3 was subjected to grinding and polishing. After that, the formed piezoelectric layer 4 was made into a complete perovskite layer, and heat treatment was performed at 650 ° C. for 5 hours in order to remove processing strain.

A copper foil for wiring was joined to the edge of the lower electrode 5a and the upper electrode 5b formed in a thin film, and connected to a drive voltage generator (not shown). After that, as shown in FIG. 2, a voltage is applied to the lower electrode 5a and the upper electrode 5b so that the adjacent electrodes have opposite signs, whereby the piezoelectric layer 4 is polarized in the atmosphere. .

In the ultrasonic actuator configured as described above, the piezoelectric layer 4 subjected to the polarization treatment is provided with a phase difference of π / 2 between the input A phase and the input B phase from the driving voltage device described above, and the alternating current is applied. It has been confirmed that when an electric field is applied as a drive voltage, a traveling wave is generated on the surface of the elastic body 3 and an elliptic motion is generated in the convex portion 3a, and the elliptic motion rotates and drives the rotor member 1.

When the rotor member 1 is rotated as described above, the piezoelectric characteristics are deteriorated or the electromechanical conversion element 4 and the elastic body 3 are reduced as compared with the conventional ultrasonic actuator formed by sticking a piezoelectric body. The adhesion strength with was not reduced.

Further, compared with the conventional ultrasonic actuator, in order to generate the same driving torque, the piezoelectric layer 4 is thinned to about 1/500, so that the driving voltage may be reduced by about 90%. did it.

(Second Embodiment) FIG. 3 is a perspective view showing a second embodiment in which the present invention is applied to an ultrasonic actuator which is an example of a vibration actuator.

In brief, this embodiment excites the elastic body by applying a drive voltage to a piezoelectric element formed on the surface of a rectangular plate-shaped elastic body (plate thickness: 3 mm). By generating the longitudinal first-order vibration mode and the bending fourth-order vibration mode in the body in a harmony manner (degeneration), the elastic body is caused to self-propagate with respect to the contacting fixed member, or the moving body in contact with the elastic body is moved. It is an embodiment applied to a driven ultrasonic actuator.

In FIG. 3, a rectangular flat plate-like elastic body 101 is provided.
A lower electrode 103a composed of a Ta layer and a Pt layer is formed in a thin film on the surface of by sputtering. This thickness is about 10 μm.

Further, the piezoelectric layer 102 is formed on the surface of the lower electrode 103a by sputtering, and the upper electrodes 103b and 103c made of Ta layer and Pt layer are formed on the surface of the piezoelectric layer 102. Piezoelectric layer 10
The formation condition of No. 2 is exactly the same as that of the first embodiment described above, and the thickness of the upper electrodes 103b and 103c is about 0.1 μm.

In this embodiment, as the piezoelectric layer 102 is formed, the first longitudinal mode of the elastic body 101 and the bending vibration 4 are generated.
Since the relationship (resonance frequency and anti-resonance frequency) with the next mode is deviated, the length of the elastic body 101 is increased after the piezoelectric layer 102 is formed so that the resonance frequency and the anti-resonance frequency of the two vibration modes match. The both ends in the direction were ground to adjust the above-mentioned deviation.

Further, in order to remove the processing strain due to the grinding process and to achieve complete perovskite formation of the piezoelectric layer 102, a heat treatment of holding at 650 ° C. for 5 hours was performed just as in the first embodiment.

The lower electrode 103 thus formed
a and copper electrodes for wiring are joined to the upper electrodes 103b and 103c, the electrodes 103a, 103b and 1
The solder foil was joined to 03c. The poling was performed in the atmosphere under the same conditions as in the first embodiment.

In the ultrasonic actuator having such a structure, when an AC voltage A phase is applied to the upper electrode 103b and an AC voltage B phase having a phase difference of 90 ° from the A phase is applied to the upper electrode 103b, protrusions are formed on the lower surface of the elastic body 101. Relative movement member (not shown) in which elliptical movement is generated at the tips of the two driving force take-out portions 101a and 101b formed in a circular shape and contacted under pressure.
A relative movement could be generated between and.

At the time of this rotation, as compared with the conventional ultrasonic actuator formed by attaching a piezoelectric material,
The piezoelectric characteristics did not deteriorate, and the adhesion strength between the electromechanical conversion element and the elastic body did not decrease.

Further, as compared with the conventional ultrasonic actuator, in order to generate the same driving torque, the piezoelectric layer 4 is thinned to about 1/500, so that the driving voltage can be reduced by 90%. It was

(Third Embodiment) FIG. 4 is a perspective view showing the structure of a third embodiment of the present invention. In the present embodiment, the second
This is an example of application to a type used in a high temperature environment in an ultrasonic actuator configured similarly to the embodiment.

That is, in this embodiment, the Curie temperature Tc of the piezoelectric layer 203 for elastic body excitation is 490.
Lead titanate (PT), which is at a temperature of 0 ° C. and is less likely to cause deterioration of polarization treatment even when used in a high temperature environment, was selected.

A lower electrode 202 made of a Ta layer and a Pt layer is formed on one plane of the elastic body 201 by sputtering, and a piezoelectric element phase 203 made of lead titanate is formed on the surface of the lower electrode 202. And an upper electrode 204 composed of a Ta layer and a Pt layer on the surface thereof.
a, 204b are formed. Upper electrodes 204a, 204
b is formed by sputtering.

Also in the present embodiment, the relationship between the longitudinal first-order vibration mode and the bending fourth-order vibration mode of the elastic body is deviated due to the formation of the piezoelectric element layer 203 made of lead titanate, so that resonance of both vibration modes is generated. The elastic body 201 was processed after the piezoelectric element layer 203 was formed so that the frequencies or the antiresonance frequencies were matched.

Further, in order to remove the processing strain due to this processing and to achieve complete perovskite conversion of the lead titanate layer, heat treatment was carried out at 650 ° C. for 5 hours as in the first embodiment. In addition, the upper electrodes 204a, 204
b. In order to bond a copper foil for wiring to the lower electrode 202, a solder foil was bonded to the electrode and heat treatment was performed at 400 ° C. in a reflow soldering furnace. The polling was performed in the air, as in the first and second embodiments.

Also in the ultrasonic actuator of the present embodiment, the AC voltage A phase and the upper electrode 20 are applied to the upper electrode 204a.
An AC voltage B phase having a phase difference of 90 degrees from that of the A phase is applied to 4b at an effective voltage of ± 10 V.
It was confirmed that an elliptic motion was generated at the tips of 01a and 201b to drive them.

At the time of this driving, as compared with a conventional ultrasonic actuator formed by sticking a piezoelectric material,
The piezoelectric characteristics were not deteriorated, and the adhesion strength between the electromechanical conversion element and the elastic body was not significantly decreased.

Further, as compared with the conventional ultrasonic actuator, in order to generate the same driving torque, the piezoelectric layer 203 is thinned to about 1/500, so that the driving voltage may be reduced by about 90%. did it.

(Fourth Embodiment) FIG. 5 is an explanatory view showing the structure of a fourth embodiment of the present invention. FIG. 5 (A) is a perspective view and FIG. 5 (B) is that of FIG. 5 (A). aa sectional view, FIG.
(C) is a bb sectional view of FIG.

In this embodiment, a piezoelectric element is used to two-dimensionally vibrate both ends or one end of a columnar elastic body to generate a progressive vibration wave on the elastic body, which travels while the drive surface rotates. The present invention is applied to an ultrasonic actuator that simultaneously gives both a linear motion and a rotary motion to a moving element that is in pressure contact with an elastic body.

As shown in FIG. 5, the piezoelectric element was formed by sputtering in a cylindrical piezoelectric element which is excited at both ends of the elastic body 301. In this ultrasonic actuator, piezoelectric elements 302 and 303 are formed at both ends of an elastic body 301, and the piezoelectric elements 302 and 30 are further formed.
3 is fixed to the stators 304 and 305, respectively. A cylindrical moving element 306 is brought into pressure contact with the outer peripheral surface of the elastic body 301.

Here, both end portions 3 of the cylindrical elastic body 301
On the surfaces of the electrodes 01a and 301b, lower electrodes 302a and 302b made of Ta and Pt layers are formed in a thin film by sputtering, and on the surfaces of the lower electrodes 302a and 302b, a piezoelectric element layer 303 made of lead zirconate titanate is formed.
a, 303b are formed, and the piezoelectric element layers 303a, 303a,
The upper silver electrode 3 is divided into four in the circumferential direction on 303b.
04a1, 304a2, 304a3, 304a4 and 3
04b1, 304b2, 304b3, 304b4 are formed.

The conditions for forming the piezoelectric element layers 303a and 303b made of lead zirconate titanate are the same as those in the first embodiment. In addition, the upper silver electrodes 304a1 to 304a4, 3
The formation of 04b1 to 304b4 was performed by screen printing.

Wiring to each electrode was performed by soldering. Further, the polarization treatment was performed in the atmosphere. In the ultrasonic actuator having such a configuration, the electrodes 304a1, 304a2, 30 of one piezoelectric element 303a are
When an AC electric field of ± 5 V with an effective voltage is applied as a drive voltage to 4a3 and 304a4 so that the phase difference between adjacent electrodes becomes π / 2 in the order shown on the left, the piezoelectric element 303a performs a swinging motion. Was confirmed.

When such a oscillating motion and also a motion having a phase difference of π / 2 with respect to that of the piezoelectric element 303a are also performed in the piezoelectric element 303b, the elastic body 30
It was confirmed that a progressive vibration wave that progresses while rotating the vibrating surface is generated in No. 1 and that the moving element 306 moves straight while rotating.

Further, in the present embodiment, the electrode 304a
1, 304a3 and 304b1, 304b3 only when the input voltage is applied, or the electrodes 304a2, 304
When a voltage is applied only to a4 and 304b2 and 304b4, a normal progressive vibration wave that proceeds without rotating the vibrating surface is generated on the elastic body 301, and the mover 306 can perform only a rectilinear motion. confirmed. Furthermore, when the elastic body was excited only by the piezoelectric element 302a and the traveling wave was absorbed by the piezoelectric element 302b, similar movement was observed.

At the time of this rotation, as compared with the conventional ultrasonic actuator formed by sticking a piezoelectric body,
The piezoelectric characteristics were not deteriorated, and the adhesion strength between the electromechanical conversion element and the elastic body was not significantly decreased.

Further, as compared with the conventional ultrasonic actuator, in order to generate the same driving torque, the piezoelectric layers 302a and 302b are thinned to about 1/500, and therefore the driving voltage must be reduced by 90%. I was able to.

(Fifth Embodiment) FIG. 6 is an exploded perspective view showing a fifth embodiment of the present invention. In the present embodiment, a non-axisymmetric bending vibration of the in-plane bending vibration of the annular elastic body is generated, and the vibrator 401 having a taper on the inner peripheral edge portion and the taper on the inner peripheral edge portion of the vibrator 401 are formed. An ultrasonic actuator including a rotor 402 that is in contact therewith.

Here, the vibrator 401 is a Ta formed by sputtering on both surfaces of a ring-shaped elastic body 401a.
Electrode 401b composed of a Pt layer and a Pt layer, and piezoelectric element layers 401c and 40 composed of lead zirconate titanate formed on the surface of the lower electrode 401b by sputtering.
1d, and a Ta layer and Pt formed on each surface by sputtering in a circumferentially divided manner
Upper electrodes 401e1, 401e2, 401e composed of layers
3, 401e4 and 401f1, 401f2, 401f
3, 401f4. The conditions for forming each piezoelectric element layer are the same as in the first embodiment.

The electrode 401e1 thus formed
To 401e4 and 401f1 to 401f4, in order to join a copper foil for wiring, a solder foil was sandwiched between the electrode and the copper foil, and heat treatment was performed at 400 ° C. in a high-frequency furnace in a pressurized state.

After that, the upper electrodes 401e1 to 401e
4, 401f1 to 401f4 and the lower electrode 401b,
As shown in FIG. 2, by applying a driving voltage so that the signs of the adjacent electrodes are opposite to each other, the piezoelectric element was polarized in the atmosphere.

Here, the upper electrodes 401e1 and 401e
2, 401e3, 401e4 and 401f1, 401f
2, 401f3, 401f4 two electrode groups,
When an AC electric field of ± 5 V with an effective voltage was applied as a driving voltage so that the phase difference between the adjacent electrodes in the order shown on the left was π / 2, the in-plane direction was applied to the inner and outer peripheral surfaces of the vibrator 401. It was confirmed that a progressive vibration wave having a driving surface was generated and the rotor in contact with the inner peripheral surface made a rotational motion.

At the time of this rotation, compared with the conventional ultrasonic actuator formed by sticking a piezoelectric element, the piezoelectric characteristics are lowered and the adhesion strength between the electromechanical conversion element and the elastic body is remarkably lowered. It never happened.

Further, as compared with the conventional ultrasonic actuator, in order to generate the same driving torque, the piezoelectric layer 4 is thinned to about 1/500, so that the driving voltage may be reduced by about 90%. did it.

(Sixth Embodiment) FIG. 7 is a perspective view showing a sixth embodiment of the present invention. The present embodiment is an actuator that utilizes displacement of a piezoelectric body in a direction perpendicular to an electric field application direction.

This actuator comprises an elastic body 501,
A lower electrode 502 made of a Ta layer and a Pt layer formed on the surface of the elastic body 501 by sputtering, a piezoelectric element 503 made of lead zirconate titanate formed on the lower electrode 502 by sputtering, and the surface thereof formed by sputtering. The upper electrode 504 is composed of the formed Ta layer and Pt layer. The conditions for forming the piezoelectric element layer made of lead zirconate titanate are the same as those in the first embodiment. In the figure, reference numeral 505 indicates the piezoelectric element 50.
It is a fixed body holding 3.

Also, the lower electrode 502 and the upper electrode 504.
In order to join the copper foil for wiring to, the solder foil is joined and pressed in a reflow soldering furnace under pressure.
A heat treatment at 0 ° C. was performed. The polling was performed in the atmosphere as in the first embodiment.

When an electric field was applied as a drive voltage to the upper electrode 504, it was confirmed that the plate-shaped portion of the elastic body 501 was vertically displaced by the displacement of the piezoelectric element layer 503 in both directions.

At the time of this rotation, the piezoelectric characteristics are not deteriorated and the adhesion strength between the electromechanical conversion element and the elastic body is not deteriorated as compared with the conventional actuator formed by attaching the piezoelectric element. It was

Further, as compared with the conventional actuator, in order to generate the same drive torque, the piezoelectric element 4 was thinned to about 1/500, so that the drive voltage could be reduced by about 90%.

(Seventh Embodiment) FIG. 8 is a perspective view showing a seventh embodiment of the present invention. The present embodiment is a mechanical filter vibrator that utilizes displacement of a piezoelectric body in a direction perpendicular to an electric field application direction.

This oscillator is composed of an elastic body 601 and an elastic body 60.
1. A lower electrode 602 made of a Ta layer and a Pt layer formed on the surface of 1 by a sputtering, a piezoelectric element layer 603 made of lead zirconate titanate formed on the lower electrode 602 by a sputtering, and formed on the surface by sputtering. The upper electrodes 604a and 604b are composed of Ta and Pt layers.

The conditions for forming the piezoelectric element layer made of lead zirconate titanate are the same as those in the first embodiment. In addition, the upper electrode 604a, the upper electrode 604b, the lower electrode 604
Then, a copper foil for wiring was joined, and heat treatment was performed at 400 ° C. in a reflow type soldering furnace in a pressurized state. The polling was performed in the atmosphere as in the first embodiment.

When an AC electric field was applied as a drive voltage to the upper electrodes 604a and 604b, the piezoelectric element layer 6
The cantilever resonance was excited in the plate-shaped portion of the elastic body 601 by the displacement of 03 in the plane direction. Furthermore, when the generated signal is detected from the upper electrodes 604a and 604b and the elastic body 601 by utilizing the fact that the induced vibration is generated on the surface of the piezoelectric element layer 603 by the resonance vibration of the cantilever, the signal is the cantilever. It was a sine wave with a frequency equal to the resonance frequency of. From this, it was confirmed that the present oscillator functions as a frequency filter (mechanical filter oscillator) that extracts only an output signal having a certain frequency from the input signal.

At the time of this vibration, as compared with the conventional frequency filter formed by attaching the piezoelectric element, the piezoelectric characteristics are deteriorated and the adhesion strength between the electromechanical conversion element and the elastic body is decreased. There wasn't.

Further, as compared with the conventional frequency filter, in order to generate the same driving torque, the piezoelectric element layer 4 is thinned to about 1/500, so that the driving voltage can be reduced by about 90%. It was

(Eighth Embodiment) FIG. 9 is a perspective view showing an eighth embodiment of the present invention and shows a basic configuration of an example in which the present invention is applied to a vibration angular velocity meter.

A rectangular parallelepiped vibrator 70 made of Ni-Cr alloy
A lower electrode 702 composed of a Ta layer and a Pt layer is formed on one side surface of No. 1 by sputtering.
On the surface of 02, a thin film 70 made of lead zirconate titanate
3 is formed as an electromechanical conversion element. Using the vibrator 701 itself as a ground electrode, an upper electrode 703 divided in three in the vibrator axial direction is formed on the lead zirconate titanate film 703 by a sputtering method. Center electrode 70
3b is used for driving, and the electrodes 703a and 703c on both sides are used for detection.

The cross section of the vibrator 701 perpendicular to the vibrator axis direction is substantially square in order to match the resonance frequencies in the driving direction and the Coriolis force direction. The conditions for forming the piezoelectric element 703 are the same as those in the first embodiment. Further, in order to join a copper foil for wiring to the electrode 702, a solder foil is sandwiched between the electrode and the copper foil, and heat treatment is performed at 400 ° C. in a reflow soldering furnace under pressure. It was The polling was performed in the atmosphere as in the first embodiment.

FIG. 10 shows the operating principle of the piezoelectric vibration angular velocity meter shown in FIG. When an AC voltage close to the resonance frequency of the vibrator 701 is applied to the driving electrode 703a,
As shown in FIG. 10A, the vibrator 701 vibrates under an unconstrained condition, and the center portion and the end portion of the vibrator have opposite velocities with respect to the vibration node 701. At this time, the oscillator 701
When the rotation about the axis occurs, as shown in FIG. 10-2, since the directions of the speeds are opposite to each other, the Coriolis force is generated in the opposite direction with the contact point of the vibration as a boundary. This force causes the vibrator 701 to bend in the in-plane direction of the electrode as shown in FIG. 10-3.

Two outer detection electrodes 703a, 703
In c, a piezoelectric signal caused by the drive signal (10-1) and a piezoelectric signal caused by the deformation (10-3) due to the Coriolis force are simultaneously generated. Among them, the piezoelectric signals due to the Coriolis force have substantially opposite phases between the two electrodes. For example, in the deformed state shown in FIG.
This is because compressive stress acts on the 03a side and tensile stress acts on the electrode 703b side, and the signs of the stress are always different between the two electrodes.

On the other hand, since the piezoelectric signals due to driving are almost the same between both electrodes, if differential signals are taken from both electrodes, almost only the piezoelectric signals due to Coriolis force can be obtained. Since the cross section of the oscillator 701 is square and the resonance frequencies in the Coriolis force direction and the driving direction are matched,
By feeding back the outputs from the detection electrodes 703a and 703c, the oscillator 701 can be driven in the vicinity of the resonance frequency with a simple oscillation circuit.

Therefore, the vibration due to the Coriolis force also resonates, and the detection sensitivity is improved. As described above, in order to match the resonance frequencies in the two directions, the demand for the shape accuracy of the vibrator 701 is extremely high. Therefore, similarly to the second and third embodiments, the resonance accuracy is adjusted after the piezoelectric element is formed. Was processed, and further heat treatment was performed at 650 ° C. to remove the processing strain.

By the way, the oscillator 701 does not necessarily have to have the same resonance frequency in the driving direction and the Coriolis force direction. Force resonance can be used. For this purpose, the oscillator may be unimorph-driven at the resonance frequency in the Coriolis force direction.

FIG. 11 shows an example of a vibrator supporting method for realizing the unconstrained vibration condition of the vibrator shown in FIG. A portion corresponding to a vibration node is fixed to the support base 705 using a silicone adhesive. Further, as a simple fixing method, it is possible to embed the entire vibrator in an adhesive having a relatively low elastic constant.

[0100]

As described above in detail, in the present invention, an electrode made of a metal having a high melting point and difficult to oxidize, a noble metal having a high melting point, or an alloy thereof is provided between the elastic body and the piezoelectric application element. Since it is configured to be arranged, even if the electrode is formed at a high temperature, or even if the electrode is formed at a low temperature and then heat-treated at a low temperature, it is possible to suppress substance diffusion between the electrode and the piezoelectric layer, It became possible to perform a sufficient heat treatment without fear of a decrease in the piezoelectric effect and peeling of the piezoelectric element.

Further, by suppressing the substance diffusion between the electrode and the piezoelectric layer, it becomes possible to sufficiently produce the crystal layer necessary for the piezoelectric, and it is possible to maximize the piezoelectric effect. It was

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a first embodiment in which a piezoelectric application element according to the present invention is applied to an ultrasonic actuator.

FIG. 2 is a plan view of the ultrasonic actuator according to the first embodiment.

FIG. 3 is a perspective view showing a second embodiment in which a piezoelectric application element according to the present invention is applied to an ultrasonic actuator.

FIG. 4 is a perspective view showing a configuration of a third exemplary embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a configuration of a fourth embodiment of the present invention.

FIG. 6 is an exploded perspective view showing a fifth embodiment of the present invention.

FIG. 7 is a perspective view showing a sixth embodiment of the present invention.

FIG. 8 is a perspective view showing a seventh embodiment of the present invention.

FIG. 9 is a perspective view showing an eighth embodiment of the present invention.

10 shows the operating principle of the piezoelectric vibration angular velocity meter shown in FIG.

11 shows an example of a method of supporting a vibrator for realizing the unconstrained vibration condition of the vibrator shown in FIG.

FIG. 12 is a graph showing an example of a difference in crystal structure based on a difference in film formation temperature or heat treatment temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotor member 2 sliding material 3 elastic body 3a convex portion 4 piezoelectric element layer 5a lower electrode 5b upper electrode

Claims (5)

[Claims] 1. A piezoelectric application element comprising an elastic body having an electromechanical conversion element formed on a surface thereof by a thin film forming technique, wherein the elastic body and the electromechanical conversion element have a high melting point and are oxidized. A piezoelectric application element characterized in that an electrode made of a difficult-to-use metal, a high melting point noble metal, or an alloy thereof is arranged. 2. The piezoelectric application element according to claim 1, wherein the piezoelectric application element is a vibration actuator. 3. The piezoelectric application element according to claim 1, wherein the piezoelectric application element is a piezoelectric actuator. 4. The piezoelectric application element according to claim 1, wherein the piezoelectric application element is a mechanical filter. 5. The piezoelectric application element according to claim 1, wherein the piezoelectric application element is a gyro.